Line width modulated display system

ABSTRACT

In a two dimensional display, the width of the line trace is modulated according to displacement in one direction of the display. Utilizing an oscilloscope as the display mechanism, for example, a plurality of closely spaced sawtooth waveforms in the vertical coordinate are utilized in producing the trace as it is scanned in the horizontal coordinate. Width modulation is obtained by modulating the beam intensity between an on and off condition.

nied States Patent 1 Wood 1 Oct. 30, 1973 [54] LINE WIDTH MODULATEDDISPLAY 3,519,876 7/1970 Murray 315/22 SYSTEM 3,573,786 4/1971 Schira315/22 [75] Inventor: David E. Wood, Schenectady, N.Y. Primary Examinercarl D. Quarfonh [73] Assignee: General Electric Company, AssistantExaminer-J. M. Potenza Schenectady, N.Y. AttorneyFrank L. Neuhauser eta1.

[22] Filed: Sept. 28, 1971 211 Appl. No.: 134,343 [571 ABSTRACT In a twodimensional display, the width of the line [52] U S 315/22 324/77 Btrace is modulated according to displacement in one [51] i 29/70direction of the display. Utilizing an oscilloscope as [58] Field A 77the display mechanism, for example, a plurality of 313/22 closely spacedsawtooth waveforms in the vertical coordinate are utilized in producingthe trace as it is he horizontal coordinate. Width modula- [56]References Clted 9 tron obtained by modulating the beam intensity be-UNlTED STATES PATENTS 2 tween an on and off condition. 3,382,436 5/1968Wil 315/2 3,440,480 4/1969 Henderson 315/18 8 Claims, 3 Drawing Figures32 5 39 SAM TOOTH 35 4y XS GENE/Z4 70/? v4 A f \l 37 55 L E C T /0/V 34/A/VE/?7'Ef? h i f 43 36 T L LEVEL DfP/VEI? COMPARATOR 0 SPECTRUM Y-AX/S1, 4 64 T5 ANALYZER DEFL EC r/o/v 1 LINE Wl/DTH DRIVE/1" 5 45 J X-AX/S46 DE F LE 6' 7' /0/V 44 I f 49% Z ,4X/$ 3/ MODULATION I 1 LINE WIDTHMODULATED DISPLAY SYSTEM This invention relates to two dimensionaldisplays, and in particular to apparatus for providing a two dimensionaldisplay having improved visual significance.

In the display art, a great deal of information is often displayedsimultaneously, thereby requiring the viewer to assimilate a largeamount of information from a relatively complex source. The task isburdensome and often tedious. Attempts to simplify the display generallyresult in a loss of information detail.

Two dimensional display devices are utilized in a wide variety of arts,wherever it is desired to compare one variable with another; forexample, a parameter (such as voltage, pH, oxygen level, literally anyparameter that can be converted via transducer into a voltage) vs. time,a parameter (such as vibration) vs. distance, or one parameter vs.another, such as amplitude vs. frequency or time vs. distance.

To consider but one of the areas wherein two dimensional displays can beenhanced, the present invention is described herein with respect tospectrum analyzers.

As is known, complex waves are produced by a wide variety of sources,e.g. the human voice, a heartbeat, and mechanical devices. In order toanalyze these complex waves, various spectrum analyzers have beendevised which provide as an output an indication of amplitude vs.frequency, generally on orthogonal coordinates. In one type of display,known as a spectrogram, a plurality of traces are spaced slightly aparton a recording medium, such as photographic film. The composite of suchtraces is then viewed in an attempt to find characteristics of aparticular complex wave source. For example, the concept of usingvoiceprints" as a means of identifying a particular person relies on thecharacteristics of each individuals voice.

However, simply displaying a plurality of adjacent traces of uniformline width, having frequency as the ordinate and amplitude as theabscissa, results in a maze of lines conveying little visualsignificance.

In an attempt to overcome this, there are provided in the prior art avariety of mechanisms for modulating the intensity of the line used totrace the amplitude vs. frequency curve. For example, in utilizing acathode ray tube as the display device, the intensity of the electronbeam is modulated in accordance with the amplitude of the signal beingdisplayed. This type of display system is encumbered at the outset bylimitations in the sensitivity of the recording medium, i.e. below acertain level the signal is not recorded and above a certain level themedium saturates or, worse, distorts the recorded indication of thesignal. Logarithmic compression of the amplitude of the recorded signalhas been used to alleviate this problem, but the result is not entirelysatisfactory.

In addition, intensity modulated displays are difficult to study fordetails of spectrum amplitude and precise time determination. Thesedifficulties can be overcome to some extent by displaying the actualspectra and expanding the time scale. However, simply doing this tendsto produce the maze of lines referred to above.

In view of the foregoing, it is therefore an object of the presentinvention to provide improved two dimensional display apparatus.

It is another object of the present invention to provide a display inwhich the display has significant overall visual impact and,simultaneously, yields detailed information.

It is a further object of the present invention to provide displayapparatus in which the display is independent of the sensitivity rangeof the display medium.

The foregoing objects are achieved in the present invention whereinapparatus is provided for modulating the line width of a display signal.In a preferred embodiment employing a cathode ray tube, for example, theline width is increased downward, i.e. in the direction of loweramplitude in an amplitude vs. frequency trace, so that the upperboundary of the trace represents actual amplitude. The width of thetrace is adjusted so that, at maximum amplitude levels, consecutivetraces almost touch. In this way, the portion of display area covered bythe trace varies in accordance with amplitude to create the visualeffect of a gray scale.

The line width modulation is specifically provided by a ramp or sawtoothgenerator coupled to the amplitude input of the display mechanism. Theline width is determined by the extent ofa plurality of closely spacedsawj tooth traces. A comparator means compares the amplitude of theinput signal to the amplitude of the sawtooth to produce a controlsignal that terminates the sawtooth trace when a particular trace lengthis obtained.

A more complete understanding of the present invention may be obtainedby considering the following detailed description in conjunction withthe accompanying drawings, in which:

FIG. 1 illustrates waveforms as produced by a display in accordance withthe present invention.

FIG. 2 illustrates apparatus in accordance with the present inventionfor producing a modulated line width display.

FIG. 3 illustrates waveforms useful in explaining the operation of thesystem of FIG. 9.

Referring to FIG. 1, there is illustrated a plurality of traces ll, 12and 13 exhibiting the trace width modulation produced by the presentinvention. A section 14 of trace 11 is enlarged in area 15 to illustratewhat the trace produced by the present invention would look like if theresolution of the display medium were exceedingly high. Specifically,the width of traces ll, 12 and 13 is modulated by modulating the heightofa plurality of sawtooth waveforms which deflect the trace in theamplitude direction. The result is a plurality of line segments 16 whichtogether form the width modulated traces illustrated in FIG. 1.

For convenience in describing the present invention, it will be assumedthat the specific display device chosen for use with the presentinvention is an oscilloscope having X-and Y-deflecting means as well asZ- axis (intensity) modulation capability. Such oscilloscopes areextremely well known in the art and are available from a variety ofmanufacturers such as Heath and Tektronix. Furthermore, it .will beassumed that the X-coordinate direction when viewing the displaycorresponds to the band of frequencies being analyzed and that theY-coordinate for a single trace corresponds to amplitude. TheY-coordinate for the plurality of traces taken together corresponds totime as noted on the ordinate of FIG. 1.

As is well known, spectrum analyzers generally comprise a mechanism forscanning a band of frequencies and producing an output signalcorresponding to the amplitude detected at the various frequencieswithin the band. Generally, where an oscilloscope is utilized as thedisplay device, the amplitude signal is coupled to the verticaldeflection system of the oscilloscope and the frequency indicatingsignal, generally a sawtooth waveform, is coupled to the horizontaldeflection system of the oscilloscope. The Z-axis input of theoscilloscope has applied thereto the amplitude signal from the spectrumanalyzer. The result is a plurality of linear traces of variableintensity which serve to indicate by a gray scale the nature of thecomplex wave applied to the spectrum analyzer.

As previously noted, in addition to being limited by the range ofsensitivity of the display medium, in this case the phosphor on the faceof the oscilloscope, This type of display cannot yield quantitativeinformation as is frequently desired.

In the present invention, the high amplitude portions of each trace arebroadened so as to provide a gray scale effect without intensitymodulating the electron beam. As will be more fully describedhereinafter, the electron beam is intensity modulated but only betweenan on and off condition so as to provide the width modulation as will bemore fully described in conjunction with FIG. 2.

FIG. 2 illustrates a preferred embodiment of the present invention forproducing a variable width trace. Generally, this embodiment of thepresent invention contains two groups of elements for producing avariable width trace. Continuing the example of an oscilloscope displaymechanism, an electron beam is usually scanned in a horizontal directionacross the face of the oscilloscope under the control ofa sawtoothwaveform. One group of elements in accordance with the present inventionprovides a second sawtooth, scanning in the vertical direction. therebyproviding a wider trace. The second group of elements in accordance withthe present invention varies the length of the vertical scans byintensity modulating the trace between an on and off condition. Theintensity modulation is carried out in accordance with the amplitude ofthe input signal. The net result is a trace that is width modulated inaccordance with the amplitude of the input signal.

Specifically, FIG. 2 illustrates line width modulating apparatus 28comprising a spectrum analyzer 30, which may comprise a conventionalspectrum analyzer producing output signals indicative of the amplitudevs. frequency characteristics of an input complex waveform, is coupledto X-axis deflection means 3] and applies thereto a signal indicative ofthe particular frequeney being analyzed. In one form of spectrumanalyzer for example where a voltage controlled oscillator is scannedacross a band of frequencies under the control of a sawtooth waveform,the signal applied to X-axis deflection means 31 may simply comprise thesawtooth waveform that is controlling the voltage controlled oscillatorwithin spectrum analyzer 30. The other output from spectrum analyzercontains the amplitude signals of the spectrum. These signals aremodified in two ways and utilized in conjunction with sawtooth waveformsproduced by sawtooth generator 32. Sawtooth generator 32 has a pair ofoutputs 33 and 34 at which there are produced retrace blanking andsawtooth signals respectively. The sawtooth signals at output 34 arecoupled by way of inverter 35 to a proportioning element 36 illustratedin FIG. 2 comprising a potentiometer. A portion of the signal appliedacross potentiometer 36 is coupled to summing network 37 where theinverted sawtooth waveform is combined with the amplitude signal fromspectrum analyzer 30. The output signal from summation network 37 isapplied to gate 38 having the other input coupled to Y-axis selector 39.The output of gate 38 is coupled to Y-axis deflection means 41 by way ofsuitable driving circuitry represented by driver 40.

The output from spectrum analyzer 30 is also applied to one input ofatwo-input summation network 43. The other input thereof is connected toline width bias means 44 whose function will be more fully explainedbelow. The output from summation network 43 is coupled to levelcomparator 42 where it is compared in amplitude with sawtooth waveformon output 34 produced by sawtooth generator 32. The output of levelcomparator 42 is coupled to one input of gate 45 which blocks or passessignals from comparator 42 to driver 48. A retrace blanking signal fromsawtooth generator 32 is coupled to the other input of gate 45. Theoutput of gate 45 is coupled to Z-axis modulation means 49 by way ofsuitable driver circuitry 48. The X-, Y- and Z- axis deflection meansare coupled to cathode ray tube display means 46.

The overall operation of the apparatus of FIG. 2 may best be understoodby considering the illustrations of FIGS. 1 and 10. It will be notedthat in FIG. I insert 15 is provided, showing in detail the verticalscannings 16 that are used to make up the variable trace width of trace11. Considering the operation of one half of the circuitry of FIG. 2,the amplitude signal from spectrum analyzer 30 is coupled to summationnetwork 37. If proportioning element 36 were adjusted so that no signalfrom sawtooth generator 32 were provided, then the output signal toY-axis deflection means 41 is approximately the same as if no tracewidth modulation apparatus were provided. That is to say, Y-axisdeflection means 41 would simply trace out the amplitude vs. frequencycharacteristic of the spectrum as provided by spectrum analyzer 30.When, however, proportioning device 36 is adjusted so that apredetermined amplitude sawtooth waveform is additively combined insummation network 37 with the amplitude signal from spectrum analyzer30, the result is a broader tracing of uniform width of the amplitudevs. frequency signals as provided by spectrum analyzer 30. What islacking is the apparatus for modulating the width of the sawtoothwaveform. This apparatus is provided by elements 42-49 in FIG. 2.

The amplitude signal from spectrum analyzer 30 is combined in summationnetwork 43 with a line width bias signal which will be assumed for themoment to be at a minimum level. The output signal from summationnetwork 43 is then compared with a sawtooth waveform in level comparator42. The operation of level comparator 42 is illustrated in FIG. 3wherein a sawtooth waveform 51 has selected points 52 and 53 indicatedthereon as indicative of the amplitude level of the signal from spectrumanalyzer 30. At points 52 and 53, the beam in the oscilloscope is cutoff, thereby darkening the short, closely spaced, vertical tracesprovided by sawtooth generator 32 through elements 35-41.

As can be seen by inspection of FIG. 3, an increase in the amplitude ofthe signal from spectrum analyzer 30 would shift points 52 and 53 to theright thereby increasing the length of time that the beam in theoscilloscope is turned on, which consequently lengthens the shortvertical traces being made as illustrated in FIG. 1 in insert 15.Conversely, as the amplitude from the signal of spectrum analyzer 30decreases points 52 and 53 move to the left thereby decreasing thelength of time that the electron beam within the oscilloscope displaymechanism is turned on.

An indicated in FIG. 3, reference numeral 54 represents the time periodwhen the oscilloscope beam is turned on. Reference numeral 55 designatesthe time period when the oscilloscope beam is turned off and referencenumeral 56 represents the retrace blanking period occurring at the endof each sawtooth. Referring again to FIG. 1, and insert 15, as the ontime of the electron beam is increased, the vertical height ofindividual scan 16 is also increased. Thus, for high amplitude signalsthe width of the trace is wider than for low amplitude signals in thespectrum.

Additional features in the preferred embodiment as illustrated in FIG. 2include inverter 35. The function of inverter 35 is to insure that theupper edge of traces ll, 12 and 13 represents the true amplitude of theamplitude signal from spectrum analyzer 30. By the insertion of inverter35, the scan produced by the sawtooth waveform from sawtooth generator32 go from the actual amplitude level of the amplitude signal to a loweramplitude level as determined by the length of time the scan ispermitted to continue by elements 42-49. Inverter 35 may be omitted, ifdesired, and the sawtooth waveform generated by generator 32 additivelycombined with the amplitude signal from spectrum analyzer 30.

Also illustrated in FIG. 2 is gate 38 coupled to Y-axis selection means39. Gate 38 serves to display successive traces so that there is nooverlap between successive traces, such as traces ll, 12 and 13 asillustrated in FIG. I. Y-axis selection means 39 may comprise anysuitable means and can comprise, for example, a stairstep voltagegenerator synchronized with the X-axis deflection so that for each scanacross the frequency band, the Y-axis deflection is raised so as to givea suitable displacement between successive traces. The amount ofdisplacement will obviously be determined by the size of the step. Thewidth of the individual trace is preferably adjusted so that for amaximum amplitude signal from spectrum analyzer 30, the successivetraces almost touch. Thus, a maximum density pattern is formed at theamplitude peaks from a plurality of successive traces.

It should not be considered that a stairstep signal from Y-axisselection means 39 is the only means by which successive traces may besuitably displaced. For example, if the output from the oscilloscope,which has been assumed for the sake of example in describing thepreferred embodiment of the present invention, is recorded on, forexample, photographic film, successive scans across the frequency bandin the X-axis direction may be suitably synchronized with incrementaladvances in the film. In such a situation the output from summationnetwork 37 would be applied directly to driver 40.

Another feature of the present invention illustrated in FIG. 2 is linewidth bias control 44. The line width bias shifts the spectrum crosssection level relative to the comparison sawtooth signal to adjust theminimum line width of the plot. The minimum may be set at zero, ifdesired, so that spectrum amplitude signals below a certain level willnot be shown at all. For the preferred embodiment of the presentinvention, the minimum line width is set at some finite value forrepresenting minimum spectrum level.

The maximum line width is obtained by adjusting the gain of the verticaldeflection system, as illustrated in FIG. 2 by control 50. The maximumwidth is adjusted so that, for maximum spectral amplitude, adjacenttraces almost touch.

The retrace blanking signal on line 33 from sawtooth generator 32 isapplied to the control input of gate 45 and prevents an output signalfrom being applied to Z- axis modulation means 49 so as to maintain thebeam of the oscilloscope in an off condition. Spurious outputs arethereby prevented during the retrace blanking period 56 as indicated inFIG. 3.

Depending upon the setting of the parameters of trace spacing and theamount of deflection for a given input amplitude, a variety of effectsis obtained. To continue the example of speech analysis, when the tracesare closely spaced and a small deflection is utilized even for highamplitude signals, a visual impression is given as to the resonanceswithin the mouth and throat of the speaker. Conversely, if wide tracespacing and large deflections are used, the visual impression createdshows the variation with time of phonation components, i.e.corresponding to the puffs of air produced by the vocal cords duringspeech.

There is thus provided by the present invention an improved twodimensional display system wherein the trace width is modulated inaccordance with trace displacement in one direction. The widthmodulation is accomplished by varying the length of a plurality oftransverse scans used to form the trace. In a specific embodiment of thepresent invention, it is shown how this is accomplished by intensitymodulating a transversely scanned sawtooth waveform in accordance withthe amplitude of an input signal.

Having thus described the invention it will be apparent to those ofordinary skill in the art that various mofiflcations can be made withoutdeparting from the spirit and scope of the present invention.

I claim:

1. A display system comprising:

input means for receiving an input signal to be displayed;

display means coupled to said input means for displaying said signal asat least one line trace;

local signal generating means for generating a comparison signal; and

comparator means for comparing the amplitude of said input signal withsaid comparison signal and providing an output signal to said displaymeans for varying the Width of said line trace as a function of saidcomparison.

2. A display system as set forth in claim 1 wherein the displacement andwidth of said line trace is proportional to the amplitude of said inputsignal, the width of said line trace producing two distinguishable edgesto said trace, and wherein the amplitude of said input signal isindicated by one of said edges.

3. A display system as set forth in claim 2 wherein said edge is thehigher amplitude edge of said line trace.

4. A display system comprising:

sawtooth generating means for producing a repetitive sawtooth waveform;

input means for receiving input signals to be displayed;

comparator means for comparing the amplitude of said input signals withsaid sawtooth waveform and producing a control signal in accordancetherewith;

blanking means coupled to and controlled by said control signal forselectively blanking the display; and

means for combining said sawtooth waveform with the amplitude of saidinput signals to produce at least one line trace of variable widthcomprising a series of closely spaced scans in the amplitude directionof the display.

5. A display system as set forth in claim 4 wherein said combining meansadditively combines said sawtooth waveform with the amplitude of saidinput signals.

6. A display system as set forth in claim 5 wherein said combining meanssubtractively combines said sawtooth waveform with the amplitude of saidinput signals.

7. A display system as set forth in claim 4 and further comprising:

proportioning means interconnecting said sawtooth generating means andsaid combining means for varying the proportion of said sawtoothwaveform in said combination of sawtooth and input signals.

8. A display system as set forth in claim 7 and further comprisingminimum trace width control means coupled to the input of saidcomparator means for establishing the minimum width of said trace.

1. A display system comprising: input means for receiving an inputsignal to be displayed; display means coupled to said input means fordisplaying said signal as at least one line trace; local signalgenerating means for generating a comparison signal; and comparatormeans for comparing the amplitude of said input signal with saidcomparison signal and providing an output signal to said display meansfor varying the width of said line trace as a function of saidcomparison.
 2. A display system as set forth in claim 1 wherein thedisplacement and width of said line trace is proportional to theamplitude of said input signal, the width of said line trace producingtwo distinguishable edges to said trace, and wherein the amplitude ofsaid input signal is indicated by one of said edges.
 3. A display systemas set forth in claim 2 wherein said edge is the higher amplitude edgeof said line trace.
 4. A display system comprising: sawtooth generatingmeans for producing a repetitive sawtooth waveform; input means forreceiving input signals to be displayed; comparator means for comparingthe amplitude of said input signals with said sawtooth waveform andproducing a control signal in accordance therewith; blanking meanscoupled to and controlled by said control signal for selectivelyblanking the display; and means for combining said sawtooth waveformwith the amplitude of said input signals to produce at least one linetrace of variable width comprising a series of closely spaced scans inthe amplitude direction of the display.
 5. A display system as set forthin claim 4 wherein said combining means additively combines saidsawtooth waveform with the amplitude of said input signals.
 6. A displaysystem as set forth in claim 5 wherein said combining meanssubtractively combines said sawtooth waveform with the amplitude of saidinput signals.
 7. A display system as set forth in claim 4 and furthercomprising: proportioning means interconnecting said sawtooth generatingmeans and said combining means for varying the proportion of saidsawtooth waveform in said combination of sawtooth and input signals. 8.A display system as set forth in claim 7 and further comprising minimumtrace width control means coupled to the input of said comparator meansfor establishing the minimum width of said trace.